In the manufacture of vehicle tires, the procedure commonly includes the forming of a carcass of the tire, separately forming a belt and tread portion of the tire, and thereafter marrying the belt and tread portion of the tire to the carcass to form a "green" tire. The green tire is thereafter treated to form the tread and various other features of the tire. In the course of one or more of the steps of the tire making procedure, other supplementary steps may be preformed such as stitching, etc.
In the forming of the belt and tread portion of the tire, it is common practice to lay down one or more layers of tire belt material (each layer comprising reinforcement cords embedded in a polymeric binder, for example) and then overlay one or more layers of strip tread material over the belt material layer(s). This combination of layers is referred to at times as a "package".
Formation of the package is accomplished on a belt and tread drum. This drum is rotatably mounted about its central longitudinal axis and the several layers that go to make up the package are laid onto the drum as it is rotated. The belt and tread package, by its inherent nature, is essentially nonexpandable radially. Accordingly, the inner diameter (circumference) of the package must be initially formed to precise specifications inasmuch as this inner diameter establishes the final "size" (i.e. diameter) of the tire. For these and other reasons, the outer circumference of the belt and tread drum must be established to the precise specifications for the tire being made.
Further, because the package formed on the belt and tread drum is essentially radially nonexpandable after being formed on the drum, to remove the completed package from the drum requires that the circumference of the drum be reduced to withdraw the drum from the package. Thus, in the prior art, belt and tread drums are made to be adjustable in circumference.
Among the problems of the prior art expandable belt and tread drums are those which relate to the adjustability of the circumference of the drum. Specifically, precise initial selection of the circumference of the drum to the required specifications has heretofore been less than desirable from the standpoints of ease, accuracy and speed of adjustment. Typically, in the prior art, the circumference of the drum is set approximately, measured using various external measurement devices, such as a "Pi" tape, and then reset, if necessary, to the desired circumference through mechanical adjustments to the drum. Several repetitions of this procedure may be required when setting the circumference of the drum to that circumference required for a particular tire size.
Prior art belt and tread drums typically include a plurality of segments, each of which has an outboard arcuate surface. The segments, collectively, define the outer circumference of the drum. Changing of the diameter of the drum (which term includes the concept of adjusting the circumference of the drum because diametral adjustment converts to circumferential adjustment in the device under consideration), is accomplished commonly by moving the several segments radially inwardly and outwardly of the drum to thereby decrease or increase the circumference of the drum.
It is therefore an object of the present invention to provide an adjustable belt and tread drum for use in vehicle tire making.
It is an object of the present invention to provide a belt and tread drum which is easily and readily adjustable of a wide range of vehicle tire diameters and which may be adjusted in circumference without disassembly of the drum.
It is another object of the present invention to provide a mechanism for precisely and readily adjusting the circumference of a belt and tread drum.